The lack of R12 availability is extremely frustrating, and in my opinion, nothing but a bunch of political b___s___!
But, like it or not, or agree with it politically or not, it's a fact we have to deal with.
Be very, very careful when selecting an alternative refrigerant. Many of these "replacements" contain explosive chemicals. "Why does that matter, it's only inside my refrigeration system", you may ask.
The reason it matters, is that a locking up compressor or other things could cause a spark. It's not worth the risk.
In the US R12 is legally available, but EXTREMELY expensive. I expect that if you explore further, you will find an expensive and legal source in Canada as well.
Best of luck,
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in